Trump's remarks were widely interpreted to be a reference to China, which is involved in 90% of North Korea's foreign trade, CNNMoney reports. Trump has previously called on China to do more to curtail North Korea's nuclear ambitions. However, experts say Beijing is unwilling to take drastic actions that could result in regime change and leave U.S. troops on China's doorstep.

But China is also the United States' largest trading partner, with exports and imports between the two countries totaling nearly $650 billion in 2016, according to the Office of the U.S. Trade Representative. Any limits on that activity could have grim consequences for American firms doing business with Beijing.

Aside from China, a few other countries trade with North Korea as well. Pyongyang also did business with India, Pakistan, Russia, Thailand and the Philippines, according to the Massachusetts Institute of Technology's Observatory of Economic Complexity citing data as of 2015. North Korea's top export destinations include China at $2.3 billion, India at $97.8 million, Pakistan at $43.1 million, Burkina Faso at $32.8 million and a handful of other Asian countries at $26.7 million. Imports largely come from China at $2.95 billion, India at $108 million, Russia at $78.2 million, Thailand at $73.8 million and the Philippines at $53.2 million.

Still, some of those figures may be out of date. India banned most trade with North Korea in April amid tougher United Nations sanctions, for instance.